tcp: tcp_tso_autosize() minimum is one packet

By making sure sk->sk_gso_max_segs minimal value is one,
and sysctl_tcp_min_tso_segs minimal value is one as well,
tcp_tso_autosize() will return a non zero value.

We can then revert 843925f33fcc293d80acf2c5c8a78adf3344d49b
("tcp: Do not apply TSO segment limit to non-TSO packets")
and save few cpu cycles in fast path.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Neal Cardwell <ncardwell@google.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Acked-by: Neal Cardwell <ncardwell@google.com>
Acked-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 7 insertions, 4 deletions

diff --git a/net/core/sock.c b/net/core/sock.c
index 29124fcdc42a..e72633c346b1 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -1581,6 +1581,8 @@ EXPORT_SYMBOL_GPL(sk_clone_lock);
 
 void sk_setup_caps(struct sock *sk, struct dst_entry *dst)
 {
+        u32 max_segs = 1;
+
         __sk_dst_set(sk, dst);
         sk->sk_route_caps = dst->dev->features;
         if (sk->sk_route_caps & NETIF_F_GSO)
@@ -1592,9 +1594,10 @@ void sk_setup_caps(struct sock *sk, struct dst_entry *dst)
                 } else {
                         sk->sk_route_caps |= NETIF_F_SG | NETIF_F_HW_CSUM;
                         sk->sk_gso_max_size = dst->dev->gso_max_size;
-                        sk->sk_gso_max_segs = dst->dev->gso_max_segs;
+                        max_segs = max_t(u32, dst->dev->gso_max_segs, 1);
                 }
         }
+        sk->sk_gso_max_segs = max_segs;
 }
 EXPORT_SYMBOL_GPL(sk_setup_caps);
 
diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c
index 841de32f1fee..e64892769607 100644
--- a/net/ipv4/sysctl_net_ipv4.c
+++ b/net/ipv4/sysctl_net_ipv4.c
@@ -702,7 +702,7 @@ static struct ctl_table ipv4_table[] = {
                 .maxlen         = sizeof(int),
                 .mode           = 0644,
                 .proc_handler   = proc_dointvec_minmax,
-                .extra1         = &zero,
+                .extra1         = &one,
                 .extra2         = &gso_max_segs,
         },
         {
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 534e5fdb04c1..190538a2a88c 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -2088,7 +2088,7 @@ static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle,
                 if (unlikely(!tcp_snd_wnd_test(tp, skb, mss_now)))
                         break;
 
-                if (tso_segs == 1 || !max_segs) {
+                if (tso_segs == 1) {
                         if (unlikely(!tcp_nagle_test(tp, skb, mss_now,
                                                      (tcp_skb_is_last(sk, skb) ?
                                                       nonagle : TCP_NAGLE_PUSH))))
@@ -2101,7 +2101,7 @@ static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle,
                 }
 
                 limit = mss_now;
-                if (tso_segs > 1 && max_segs && !tcp_urg_mode(tp))
+                if (tso_segs > 1 && !tcp_urg_mode(tp))
                         limit = tcp_mss_split_point(sk, skb, mss_now,
                                                     min_t(unsigned int,
                                                           cwnd_quota,